Compressor HVAC: Description and Operation

The compressor for air conditioning is belt driven by the engine. The A/C Compressor Clutch engages and disengages the compressor to remove the air conditioning load from the engine when needed. The A/C Compressor Control Clutch engages the compressor when the A/C mode selector is in MAX, NORM, BI-LEVEL, DEFOG or DEFROST. The V6 VIN L Compressor will cycle on and off when in use.

The A/C Compressor Clutch Diode connected across the A/C Compressor Clutch suppresses high voltage spikes that are generated by the collapsing magnetic field of the clutch coil when the clutch is turned off.

The A/C Compressor Relay opens and closes the circuit to the A/C Compressor Clutch. The coil of the relay is grounded by the Electronic Control Module (ECM). This enables the ECM to disengage the air conditioning to reduce the load on the engine when required. Wide open throttle, high power steering pressure or coolant temperature will also prevent the A/C system from engaging.

The ECM also receives an air conditioning ON signal, which is battery voltage from the Heater And A/C Control Assembly. It signals the ECM that A/C compressor operation is required. This voltage is applied through the A/C High Pressure Switch and the A/C Cycling Pressure Switch in the V6 VIN L engine.

In the V6 VIN T engine, the ECM monitors a signal voltage from the A/C Pressure Sensor. If either a low or high refrigerant pressure condition occurs, the ECM will prevent the A/C Clutch from engaging.